Temperature management system and method for burn patients

ABSTRACT

Intravascular closed loop heat exchange catheters are used to manage temperature in burn patients.

FIELD OF THE INVENTION

The present invention relates generally to patient temperature controlsystems.

BACKGROUND OF THE INVENTION

It has been discovered that the medical outcome for a patient sufferingfrom severe brain trauma or from ischemia caused by stroke or heartattack or cardiac arrest is improved if the patient is cooled belownormal body temperature (37° C.). Furthermore, it is also accepted thatfor such patients, it is important to prevent hyperthermia (fever) evenif it is decided not to induce hypothermia. Moreover, in certainapplications such as post-CABG surgery, it might be desirable to rewarma hypothermic patient.

As recognized by the present invention, the above-mentioned advantagesin regulating temperature can be realized by cooling or heating thepatient's entire body. Moreover, the present invention understands thatsince many patients already are intubated with central venous cathetersfor other clinically approved purposes anyway such as drug delivery andblood monitoring, providing a central venous catheter that can also coolor heat the blood requires no additional surgical procedures for thosepatients. The following U.S. patents, all of which are incorporatedherein by reference, disclose various intravascularcatheters/systems/methods: U.S. Pat. Nos. 6,749,625, 6,786,916,6,581,403, 6,454,792, 6,436,130, 6,146,411, 6,109,783, 6,419,643,6,416,533, 6,409,747, 6,405,080, 6,393,320, 6,368,304, 6,338,727,6,299,599, 6,290,717, 6,287,326, 6,165,207, 6,149,670, 6,146,411,6,126,684, 6,306,161, 6,264,679, 6,231,594, 6,149,676, 6,149,673,6,110,168, 5,989,238, 5,879,329, 5,837,003, 6,383,210, 6,379,378,6,364,899, 6,325,818, 6,312,452, 6,261,312, 6,254,626, 6,251,130,6,251,129, 6,245,095, 6,238,428, 6,235,048, 6,231,595, 6,224,624,6,149,677, 6,096,068, 6,610,083, 6,042,559, and U.S. patent applicationSer. No. 10/355,776.

As understood herein the control of body temperature for burn patientsis also important, e.g., it would be advantageous to prevent fever inburn patients and/or to prevent eaccidental therapeutic hypothermia inburn patients. For example, heat loss is a common finding in burnedvictims Severe hypothermia during operation of debridement of bum wound,especially when patients are sedated and mechanically ventilated, isassociated with increased mortality and morbidity. Studies showed almost100% mortality in severely burned patients who presented with coretemperature less than 32° C. The present invention recognizes thatcurrent therapeutic approaches such as warm blanket are limited.

SUMMARY OF THE INVENTION

A method includes advancing a closed loop intravascular heat exchangecatheter into the vasculature of a burn patient, and establishing adesired patient temperature using the catheter. The catheter may be usedto warm the patient during skin graft surgery, as well as to establishnormothermia in the patient should the patient become febrile.

In non-limiting implementations the catheter has plural heat exchangeelements. In one-non-limiting embodiment the heat exchange elements areballoons. In another embodiment the heat exchange elements are metal. Inyet another embodiment they are established by plural heat exchangefluid return tubes communicating with a central supply lumen at a distalend of the catheter for carrying heat, exchange fluid. In this lastembodiment each return, tube is formed spirally around the supply lumensuch that a body fluid flowing past the return tube exchanges heat withthe heat exchange fluid flowing therein.

In another aspect, a system for treating a burn patient includes aheater/chiller and an intravascular catheter configured for receivingworking fluid from the heater/chiller and returning working fluidthereto in a closed loop. A substrate is provided bearing instructionsfor using the catheter to establish a desired patient temperature in thepatient.

In yet another aspect, a method for treating a burn patient includesconducting skin graft surgery on the patient, and during surgery,countering hypothermia in the patient using a catheter.

The details of the present invention, both as to its structure andoperation, can best be understood in reference to the accompanyingdrawings, in which like reference numerals refer to like parts, and inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a system according to presentprinciples;

FIG. 2 is a perspective view of a first non-limiting catheter,schematically showing a medicament source and coolant source in anexploded relationship with the catheter;

FIG. 3 is a perspective view of a second non-limiting catheter;

FIG. 4 is a cross-section as seen along the line 4-4 in FIG. 3;

FIG. 5 is a side view of a portion of a third non-limiting catheter; and

FIG. 6 is a cross-section of the, catheter shown in FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially to FIG. 1, a system, generally designated 10, isshown for managing and otherwise controlling whole body temperature of aburn patient 12. The system 10 may be used to establish normothermia inthe burn patient 12, i.e., to prevent undesired hypothermia during,e.g., surgery or to prevent hyperthermia in the patient, and/or thesystem 10 may be used to therapeutically cool the patient 12 to ahypothermic state, e.g., moderate hypothermia around thirty four degreesCelsius. In some implementations discussed below, the system 10 may alsobe used to provide central venous access to the burn patient 12. Innon-limiting implementations the burn patient 12 may be treated with thesystem upon a predetermined burn threshold, e.g., the body temperatureof the burn patient 12 may be managed using the system 10 in the eventthat the bum patient 12 has suffered third degree burns over thirtypercent or more of the patient's body, it being understood that thispercentage is not limiting on present principles.

As shown,, the system 10 includes an intravascular closed loop heatexchange catheter 14 that receives a heat exchange fluid (also referredto herein as “coolant”) from a heater/chiller 16, with the fluidcirculating in a closed loop. The fluid can be saline or other fluidsuch as refrigerant. Either the fluid flow rate and/or the temperatureof the fluid is controlled by a controller associated with theheater/chiller 16 based on a patient temperature feedback signal tocontrol the amount and if desired the rate at which heat is added orsubtracted from the patient. The controller can be implemented by asoftware-executing processor or by discrete logic circuits or otherelectronic circuitry device to establish a desired patient temperatureby appropriately controlling the flow rate and/or heat exchanger inresponse to a temperature signal derived from a sensor in the patient12. Non-limiting examples of heater/chillers that can be used aredisclosed in U.S. Pat. Nos. 7,101,388; 6,878,156; 6,786,916; 6,454,792;6,454,792; 6,146,411; and 6,019,783, all of which are incorporatedherein by reference. Further examples of non-limiting heater/chillersare shown in U.S. Pat. Nos. 6,581,403, 6,436,130, and 6,109,783,incorporated herein by reference.

As also shown in FIG. 1, in some non-limiting implementations at leasttwo central venous (CV) components can be in communication with thecatheter 16 for undertaking central venous functions in addition tocontrolling the temperature of the patient. These functions include andare not limited to drug infusion and blood extraction for bloodmonitoring, as well as blood pressure monitoring. For instance, a bloodmonitor 18 can communicate with the catheter 14 via a line 20 to monitorblood pressure or withdraw blood from the central venous system of thepatient 12. Also, a syringe 22 can engage the catheter 14 via aconnector line 24 for infusing drugs or other medicament such asepinephrine into the patient 12. The components 16, 18, 22 can all beconnected to the catheter 14 via a proximal connector hub 26 of thecatheter 14. The hub 26 can be formed with a suture anchor 28 or otheranchor structure such as tape for providing a means to fasten thecatheter 14 to the skin of the patient 14 for long-term use.

The catheter 14 may be any suitable closed loop intravasculartemperature control catheter including without limitation in addition tothe specific structures disclosed herein, the catheters disclosed in thefollowing U.S. patents, all incorporated herein by reference: U.S. Pat.Nos. 5,486,208, 5,837,003, 6,110,168, 6,149,673, 6,149,676, 6,231,594,6,264,679, 6,306,161, 6,235,048, 6,238,428, 6,245,095, 6,251,129,6,251,130, 6,254,626, 6,261,312, 6,312,452, 6,325,818, 6,409,747,6,368,304, 6,338,727, 6,299,599, 6,287,326, 6,126,684.

In any case, once the patient 12 has been diagnosed as suffering skinburns sufficient to warrant management of the temperature of the patient12, the catheter 12 may be placed in the venous system, e.g., in thesuperior or inferior vena cava without blocking the vessel so that bloodcan flow around the catheter to effect, heat exchange. In non-limitingembodiments the catheter 14 may be advanced (possibly through anintroducer sheath) into the vena cava of the patient 12 through a groinentry point 32 or through a neck entry point 34 to the central venoussystem of the patient 12. When advanced through the groin the catheteris advanced either through the saphenous vein or femoral vein to theinferior vena cava, and when advanced through the neck through thejugular or subclavian vein to the superior vena cava or inferior venacava. Less desirably, the catheter 14 may be advanced into the arterialsystem of the patient 12.

Once disposed in the bloodstream of the patient 12, a target patienttemperature is input to the heater/chiller 16. The target temperaturecan be, e.g., normothermia (i.e., approximately thirty eight degreesCelsius), in which case the heater/chiller 16 controls the temperatureand/or flow rate of the coolant circulating through the catheter 14 inresponse to a patient temperature signal as appropriate to heat or coolthe patient to achieve and maintain target temperature. It is to beunderstood that the patient temperature signal may be generated by asensor on the catheter 14 and sent to the heater/chiller 16. Or thesensor may be on another device that can be electrically connected tothe heater/chiller 16 for sending a patient temperature signal thereto.For example, the sensor may be on a Foley catheter, a rectal temperatureprobe, an esophageal probe, a tympanic temperature device, or othersuitable patient temperature generating device.

Or, target temperature may be below normothermia for the purpose oftherapeutically establishing mild or moderate (or even deeper)hypothermia in the patient, in which case the heater/chiller 16 removesheat from the coolant as necessary to achieve and maintain hypothermiafor a therapeutic amount of time.

Now referring to FIG. 2 for a description of a first non-limitingcatheter 14, commencing at the proximal end the heater/chiller 16provides coolant such as saline through a coolant supply line 36, andcoolant is returned from the catheter 14 via a coolant return line 38.The non-limiting catheter 14 includes a source tube 40 terminating in afitting such as a female luer fitting 42. Also, the catheter 14 has areturn tube 44 terminating in a fitting such a male luer fitting 46. Thefittings 42, 46 can be selectively engaged with complementary fittings48, 50 of the lines 36, 38 to establish a closed circuit coolant pathbetween the catheter 14 and heater/chiller 16.

Additionally, the non-limiting catheter 14 shown in FIG. 2 may includethe primary infusion tube 20 as mentioned above that can also be used asa guidewire tube. The tube 20 terminates in a fitting such as a femaleluer 52. A guide wire 54 or the syringe 22 shown in FIG. 1 can beadvanced through the tube 20 in accordance with central venous catheterplacement principles, or the monitor 18 shown in FIG. 1 may be engagedwith the tube 20.

Moreover, the connector line 24, which can establish a secondaryinfusion tube, can end in a female luer fitting 56 that can beselectively engaged with, e.g., the syringe 22 for infusing fluid fromthe syringe or other source such as an IV bag into the patient.

The tubes 20, 24, 40, 44 are held in the hub 26, which may be distallytapered as shown. As set forth in U.S. Pat. No. 6,368,304, incorporatedherein by reference, the hub 26 establishes respective pathways forfluid communication between the tubes 20, 24, 40, 44 and respectivelumens in the body 46 of the catheter 14. The suture anchor 28advantageously may be formed on the hub 26 for suturing the catheter 14to a patient in accordance with central venous catheter operatingprinciples.

The non-limiting the catheter body 46 may include at least two lumens,and in a preferred embodiment the catheter body 46 includes at leastfour lumens and, more preferably has five lumens. Two of the lumens arecoolant supply and return lumens through which coolant is circulated toand from one more distally-located, axially-spaced thin-walled heatexchange membranes 66, 68 (two shown) that are arranged along the lastfifteen or so centimeters of the catheter body 46 and are bonded to theouter surface of the catheter body 46, with an infusion port 64 beinglocated between the heat exchange membranes 66, 68. Essentially, theheat exchange membranes 66, 68 extend along most or all of that portionof the catheter 46 that is intubated within the patient. The heatexchange membranes can be established by a medical balloon material.When coolant is circulated through them the heat exchange membranes maydefine a diameter of about ten French, and preferably no more thantwelve French in non-limiting embodiments. Thus, the heat exchangemembranes 66, 68 are relatively long and comparatively thin, toadvantageously avoid excessively blocking blood flow through the venacava while nevertheless effecting patient cooling. If desired, atemperature sensor 70 such as a thermistor or other suitable device canbe attached to the catheter 14 as shown by solvent bonding at a pointthat is proximal to the membranes 66, 68. The sensor 70 provides patienttemperature feedback to the heater/chiller 16 through a wire disposed inthe catheter 14. Or, the sensor 70 can be disposed in a lumen of thecatheter 14, or attached to a wire that is disposed in a lumen of thecatheter 14, with the sensor hanging outside the catheter 14.Alternatively, a separate temperature probe can be used, such as anesophageal probe, a rectal probe or tympanic temperature sensor.

FIGS. 3 and 4 show another non-limiting intravascular closed loop heatexchange catheter that can be used, generally designated 114. As shownin FIG. 3, the catheter 114 can include plural heat exchange elements130. The heat exchange elements 130 can be established by one or moremetal, preferably gold, hollow elongated segments that have externalsurfaces which have turbulence-inducing irregular exterior surfaces thatare shaped to induce gentle turbulence in blood flowing past theelements. Separating adjacent heat exchange elements 130 can be aflexible articulating joint 131, it being understood that the heatexchange elements 130 and joints 131 can be formed from a single pieceof material such as plastic or metal, e.g., gold. The details of theheat exchange elements 130 and their configuration are set forth in U.S.Pat. Nos. 6,554,797 and 6,096,068, incorporated herein by reference. Inany case, coolant is circulated in a closed fluid communication loopbetween the heat exchange elements 130 and heater/chiller 16 to removeheat from the patient 12 or to add heat to the patient to rewarm thepatient.

Now referring to FIG. 4, it can be seen that in non-limitingimplementations the catheter 114 if desired may establish a tubularconduit that is disposed substantially coaxially within the heatexchange. elements 130, with the conduit having a supply lumen 136 forsupplying a pressurized working fluid (represented by arrows 138) to adistal end 140 of the catheter 114. As the fluid exits the supply lumen138, it flows out and around the supply lumen 138 in a proximaldirection as shown in an annular return lumen 142. It may readily beappreciated that heat is exchanged between the fluid 138 and bloodstreaminto which the catheter 114 is placed across the walls of the heatexchange elements 130 to heat or cool the patient as desired.

In addition to the supply and return lumens 136, 142, the catheter 114if desired may have at least two and possibly more infusion or workinglumens (only two shown for clarity) for undertaking CV functionssimultaneously with controlling patient temperature. Specifically, asshown in FIG. 4, a first infusion or working lumen 144 terminates in afirst outlet port 146, and a second infusion or working lumen 148terminates in a second outlet port 150. Both lumens 144, 148 areseparated from the fluid 138 and both lumens 144, 148 preferably extendto the hub 26 shown in FIG. 1. The second infusion or working lumen 148can be coaxial with the body of the catheter 114 as shown. The secondport 150 can be located on the distal tip of the catheter 114 as shovvn.In any case, to provide for mixing of infused drugs in the bloodstreamif two drugs are to be administered, the ports 146, 150 arelongitudinally separated from each other as shown. With the above inmind, the monitor 18 (FIG. 1) or other CV device such as an infusiondevice can communicate with one of the infusion or working lumens 144,148 while the syringe 22 can communicate with the other infusion orworking lumen 148, 144.

As an alternative to the catheters 14, 114, a catheter 214 shown inFIGS. 5 and 6 and disclosed in U.S. Pat. Nos. 6,585,692 and 6,610,083,both of which are incorporated herein by reference, may be used. Thecatheter 214 can include plural heat exchange elements 230. The heatexchange elements 230 can be established by, e.g., three coolant returntubes made of hollow plastic, with each tube establishing a respectivecoolant return lumen. As shown best in FIG. 6, a central coolant supplylumen 232 that is established by a center tube 234 is also provided. Itis to be understood that the supply lumen 232 conveys coolant from theheater/chiller 16 in a distal direction along the catheter 214, whereasthe heat exchange elements 230 (the coolant return tubes) convey coolantback to the heater/chiller 216 in a proximal direction as indicated bythe arrows 236 in FIG. 5. With this structure, blood 238 in a centralvenous system vein 240 into which the catheter 214 is advanced is cooled(or heated) by exchanging heat with the coolant across the walls of theheat exchange elements 230. Thus, coolant is circulated in a closedfluid communication loop between the heat exchange elements 230 andheater/chiller 16 to remove heat from the patient or to add heat to thepatient to rewarm the patient after surgery or after the termination oftherapeutic hypothermia treatment.

The coolant return tubes are spirally formed around the center tube 234,and can be adhered thereto or not. That is, non-limiting heat exchangeelements 230 define spirals. The length “L” of the heat exchange regionof the catheter 214 can be about 250 millimeters, with the pitch of thespiral heat exchange elements 230 being about 64 millimeters. In anycase, the coolant supply lumen 232 terminates in a hollow distal tip, asdo the lumens of the heat exchange elements 230. Accordingly, coolantpasses from the supply tube to the return tubes at the distal tip.

Additionally, as best shown in FIG. 6, the center tube 234 can establishone or more working lumens (only two shown in FIG. 6 for clarity ofdisclosure) for undertaking CV functions simultaneously with controllingpatient temperature. In the embodiment shown, the center tube 234establishes first and second working lumens 244, 246 that have anysuitable cross-sectional shape and that can respectively communicatewith the central venous components 18, 22 discussed above. Both workinglumens 244, 246 are separated from the coolant and both working lumenspreferably extend to the hub 26 shown in FIG. 1. The working lumens 244,246 can terminate in respective exit ports that may be longitudinallyspaced from, each other, e.g., one port can be at the distal tip of thecatheter 214 and the other port can be located somewhat proximal to thetip.

Any of the catheters disclosed herein can be used to maintainnormothermia in the burn patient 12, typically by warming the patient.For example, the catheters 14, 114, 214 can be used during surgery tokeep patient temperature above 36 C when replacing necrotic skin withgrafts. Without the present invention, it is often the case that patienttemperature drops so that only one limb at a time may be repaired withgrafts, but with the present invention grafts on all limbs may becompleted during the same surgery.

Temperature management of the patient 12 may be maintained after surgeryusing the system 10 for, e.g., thirty days, with a catheter change everyfew days if desired, with the patient in the burn unit and/or hospitalICU.

In one non-limiting treatment protocol, the patient is older than 18years and presents with a core temperature of under 37° C. Targettemperature can be set to 36.5° C. and warming rate to maximum. A coretemperature monitor is established by, e.g., placing anesophageal/Foley/rectal temperature probe in the patient, with themonitor connected to the heater/chiller 16. Warming is commenced asearly as possible to prevent core temperature drop. The catheter 14 canalso be used as a multi-lumen central venous catheter to deliver warmfluid such as saline, medications, to withdraw blood or conduct othermonitoring acts of patient parameters. All of these steps can take placeduring and after skin graft surgery. Subsequently, should the patientdevelop fever, the catheters 14, 114, 214 can also be used to controlhyperthermia. A substrate 300 (FIG. 1) may be provided that bearsinstructions for using the present catheter to establish a desiredpatient temperature in the burn patient 12 in accordance with principlesset forth herein.

While the particular temperature management system and method for burnpatients is herein shown and described in detail, it is to be understoodthat the subject matter which is encompassed by the present invention islimited only by the claims.

1. A method comprising: advancing a closed loop intravascular heatexchange catheter into the vasculature of a burn patient; andestablishing a desired patient temperature using the catheter, whereinthe catheter includes plurral heat exchange elements established by oneor more hollow elongated segments that have external surfaces which haveturbulence-inducing exterior surfaces that are shaped to alter the flowof blood flowing past the elements.
 2. The method of claim 1, whereinthe catheter is used to warm the patient during skin graft surgery. 3.The method of claim 2, wherein the catheter is used to establishnormothermia in the patient should the patient become febrile. 4,5.(canceled)
 6. The method of claim 1, wherein the heat exchange elementsare metal. 7-14. (canceled)
 15. A method for treating a burn patientwhile skin graft surgery is being conducted on the patient, comprising:during surgery, circulating working fluid through a catheter in thepatient to counter hypothermia in the patient; and controlling thetemperature of the working fluid.
 16. The method of claim 15, whereinthe catheter is used to establish normothermia in the patient should thepatient become febrile.
 17. The method of claim 15, wherein the catheterhas plural heat exchange elements.
 18. The method of claim 17, whereinthe heat exchange elements are balloons or are metal.
 19. The method ofclaim 15, comprising using the catheter to undertake at least onecentral venous line function selected from the group consisting of:infusing medicament into the bloodstream, infusing saline into thebloodstream, and monitoring a patient parameter.
 20. The method of claim19, wherein the act of countering hypothermia is executed by circulatingworking fluid through the catheter such that the working fluid does notenter the bloodstream and exchanges heat therewith.
 21. The catheter ofclaim 1, wherein the heat exchange elements are made of gold.
 22. Thecatheter of claim 1, wherein adjacent heat exchange elements areseparated by a flexible articulating joint.
 23. The catheter of claim 1,wherein the heat exchange elements are made of single piece of material.24. The catheter of claim 1, wherein the heat exchange elements are madeof plastic.
 25. The catheter of claim 1, wherein the heat exchangeelements are spiral.
 26. The catheter of claim 1, wherein the heatexchange elements are fluted.